It's Christmas. HOORAY! But something strange happens.

Pinkie Pie was missing during Christmas. So was Applejack and Twilight. The next day, the Cutie Mark Crusaders. Then Fluttershy. Finally, only Rainbow Dash is left. But then she nearly goes over the line.

Who could have done this? And why did he or she choose it at this time of year? And even more important, what has happened to everyone?